The sections containing ventral tegmental area (VTA), nucleus accumben (NAc), periaqueductal gray (PAG), amygdala (AMG) and hippocampus CA1 (HIPCA1) were selected and the mRNA levels of PENK were investigated by in situ hybridization.

• 末次注射后3h取脑并冰冻切片,留取中脑腹侧被盖区(VTA)、伏隔核(NAc)、中脑导水管灰质(PAG)、杏仁核(AMG)、海马CA1区(HIPCA1)的切片。